为什么else语句不适用于isset？

Question

I found something strange happening with this:

if(isset($_POST['name'])){
    echo $_POST['name'];
}
else{
    echo "please enter name";
}

in the above example the else statement does not work.

if(empty($_POST['name'])){
    echo "please enter name";
}
else{
    echo $_POST['name'];
}

but when I do it like this, it works. Can anybody tell me why this is happening?

Answer 1

I'm assuming you are submitting a form, where the field name is empty, but it exists (or in other words isset).

The difference between isset and empty is, that the latter assumes that $_POST['name'] exists, but contains an empty value, e.g. "" or 0, whereas the first only checks if $_POST contains an element name.

When your form contains a field, it will be submitted and therefore is set, whether it has any contents or not (i.e. is empty).